A metabolic stress test, also called a cardiopulmonary exercise test (CPET), measures the response of the lungs and heart to exercise. This test measures the stages of oxygen and carbon dioxide in the blood and shows how much air the lungs can absorb. It is useful for people with heart failure, COPD, and many other conditions.

What is a Metabolic Stress Test?

A metabolic stress test involves exercising on a stationary bicycle or treadmill under the supervision of a physician. It is the gold standard for measuring cardiorespiratory fitness (CRT). CRT measures the ability of the heart, lungs, and blood pots to deliver oxygen to the muscles during physical activity.

You may have heard your doctor refer to this test as a cardiopulmonary exercise test (CPET). This is because it assesses the function of the heart (cardio) and lungs (pulmonary) simultaneously. This test helps doctors diagnose and treat various medical situations, such as heart failure and chronic obstructive pulmonary disease (COPD). It also helps doctors determine your prognosis, or expected outcome, given that you have one or more chronic medical conditions.

Cardiopulmonary Exercise Test and Stress Test

A metabolic (cardiopulmonary) exercise test assesses the health of your heart and lungs. It is different from a stress test that a cardiologist might order. Both tests involve cycling or running on a treadmill while technicians observe and record your data. However, with a metabolic stress test, you breathe through a special device (a mask or mouthpiece). This device measures the amount of oxygen and carbon dioxide in the air you exhale, as well as the amount of air your lungs can inhale.

You can think of a metabolic stress test as a full-featured stress test. Your technician connects you to more equipment than a standard stress test, and as a result, the test provides much more data. This data helps your pulmonologist, cardiologist, and other specialists understand how your heart and lungs respond to exercise.

What does a metabolic (cardiopulmonary) stress test show?

A metabolic stress test shows which cardiovascular or pulmonary conditions limit your ability to exercise. If you have shortness of breath or chronic fatigue, a metabolic stress test can help determine the cause of the problem.

Your healthcare provider may order this test to:

• Determine why you have exercise intolerance (why you feel short of breath or very tired during physical activity).
• Determine how much stress your heart and lungs can handle.
• Diagnoses cardiovascular and pulmonary conditions.
• Determine the severity of your condition and provide a prognosis.
• Assess your risk of complications before major surgery.
• Create a treatment plan.
• Check your body’s response to treatment.
• Evaluate your progress with exercise training (such as cardiac rehabilitation).
• Help you develop a safe and actual exercise program.

Who needs a Metabolic (Cardiopulmonary) Stress Test?

Your healthcare provider will control if you need this test. It is generally appropriate for children 10 years and older and adults of all ages.

Doctors order metabolic stress tests to diagnose and treat the following conditions:

• Asthma.
• Chronic obstructive pulmonary disease (COPD).
• Cystic fibrosis.
• Heart failure.
• Interstitial lung disease.
• Lung cancer.
• Primary ciliary dyskinesia.
• Pulmonary arterial hypertension (PAH).
• Sarcoidosis.

Doctors also order metabolic stress tests before certain surgeries, such as:

• Lung resection.
• Lung transplantation and heart-lung transplantation.
• Lung volume reduction surgery (LVRS).
• Other major thoracic surgeries.

Cardiopulmonary Exercise Testing for Heart Failure

Cardiopulmonary exercise testing (CPET) is a key tool doctors use to help patients with heart failure. This test assesses your breathing and accurately determines how much oxygen you can inhale at any given time. The results of this test show the severity or stage of your heart failure and help guide your treatment plan.

Who Should Not Undergo Metabolic Exercise Testing (MEET)?

There are several reasons why it is not safe to undergo this test. Healthcare professionals refer to these as “contraindications.”

This test may not be safe if you have:

• An acute infection (such as a cold or the flu).
• Acute myocarditis or pericarditis.
• A recent myocardial infarction (within the past 30 days).
• Deep vein thrombosis (DVT) in the legs.
• Hypertrophic cardiomyopathy.
• Kidney failure.
• Moderate to severe valvular stenosis.
• Late pregnancy or pregnancy with complications. Severe hypertension.
• Severe pulmonary arterial hypertension (PAH).
• Uncontrolled arrhythmias.
• Uncontrolled heart failure.
• Unstable angina.

About the Test

How to Prepare for the Test

Follow your healthcare professional’s instructions to prepare for the metabolic stress test. Here are some general guidelines:

Avoid any product containing caffeine for 24 hours before the test. Caffeine can interfere with test results. Caffeine is found in coffee, tea, soda, and chocolate. Traces are also found in strawberries and any product labeled “caffeine-free.”

Do not eat or drink anything other than water for four hours before the test. Do not smoke or vape for eight hours before the test (ideally 24 hours). Nicotine can affect test results.

Do I need to take any medication on the day of the test?

Ask your doctor if you need to adjust your medication schedule. In general, you should avoid taking any over-the-counter medications containing caffeine for 24 hours before the test. These include some diet pills, NoDoz®, Excedrin®, and Anacin®.

Guidelines for People with Diabetes

If you take insulin to switch your blood sugar, ask your doctor what dose you should take on the day of the test. Doctors usually recommend taking only half of your usual morning dose and a light breakfast four hours before the test.

If you take pills to switch your blood sugar, wait until after the test to take your medication.

What should you wear on the day of the test?

Wear comfortable clothing that allows you to change freely. It’s also recommended to wear light clothing (such as a tank top or a light cotton blouse), as you will sweat a lot. You can wear this clothing to your appointment or to change into after the test. Also, be sure to wear comfortable shoes (such as sneakers).

You will have access to a locker during the test to store your belongings. However, it is recommended to leave valuables at home.

How is a Metabolic (Cardiopulmonary) Exercise Test Performed?

The test will be performed in a stress lab (a room where stress tests are performed). A lab technician will perform the test under the supervision of a physician. You will be asked to exercise on a stationary bike or walk on a treadmill. The stationary bike is the most common method. Your doctor will control the best method for you based on your age, overall health, fitness level, and other factors.

During the exercise, you will breathe into a device that measures your breathing. You will use a mask or a mouthpiece, and you can choose the device that is most comfortable for you.

The exam will consist of the following steps:

• Electrocardiogram (ECG) connection: The technician will place electrodes (small, flat stickers) on different areas of your chest. These electrodes are connected to a monitor that records your heart’s electrical activity during the exam.
• Resting phase: This usually lasts three minutes. The technician will help you familiarize yourself with the mask or mouthpiece, and you will begin breathing through it. The technician will measure your vital signs, including your blood pressure and blood oxygen level. Your heart rate will also be monitored on the ECG monitor. If you need arterial blood gases (to check your blood oxygen and carbon dioxide levels), the technician will insert an arterial line. This is a small tube inserted into an artery in your arm (the radial artery) and collects blood samples periodically throughout the test.
• Warm-up phase: This usually lasts two to three minutes. “No load” means you are cycling or walking without any resistance. Your technician collects information about your “active baseline.” This is how your heart and lungs respond to the lowest possible level of exertion.
• Progression phase: This typically lasts eight to twelve minutes. You cycle or walk steadily, without stopping, as your technician gradually increases the resistance on the machine. It will become increasingly difficult to continue. At this point, your technician will ask you to report how you feel. It is important to cycle or walk for as long as possible.
• Cool-down phase: This lasts three to five minutes. You cycle or walk without resistance, just as you did at the beginning. Your technician will check your vital signs and measure how quickly your heart rate recovers. Once your heart rate and blood pressure return to normal, you can prepare for the test.

Rate of Perceived Exertion (RPE) Scale

During the test, you report how you feel using the Degree of Perceived Exertion (RPE) scale. There are several possible RPE scales used by healthcare professionals. The most common way to measure CPET is to raise your fingers and rate shortness of breath and leg tiredness on a scale of 0 to 10. The higher the number, the more tired you feel.

All equipment collects a wealth of data about what’s happening inside your body, but only you can know how you feel. Therefore, it’s important to ask the technician any questions you have about the scale before beginning.

 How will I Feel During the Test?

To get the most accurate and useful results, you should exercise to the point of exhaustion. It is normal for your heart rate, blood pressure, and breathing rate to increase. You will also experience sweating and your legs will become increasingly tired. You may have a dry mouth from breathing through the mouthpiece.

This is exercise and will feel like it. However, if you experience any unusual symptoms during the test, stop exercising and report them to your technician immediately. These symptoms include:

• Pain, discomfort, or tightness in your chest, arm, or jaw.
• Severe shortness of breath.
• Dizziness or lightheadedness.

These symptoms may be signs of a heart attack or other medical emergency. Technicians will watch for any concerning changes on the EKG monitor and, if necessary, stop the test immediately.

How long does the test take?

Your appointment will last approximately 75 minutes. In fact, your workout will last up to 20 minutes, including your warm-up and cool-down.

Results and Next Steps

How do I get my test results?

Your healthcare provider will let you know when and how you can see your results. You’ll likely see them in your electronic health record and will also meet with your healthcare provider to discuss them.

This test records thousands of measurements in a format known as a nine-panel chart. This is a series of complex and technically sophisticated graphs that show detailed information about how your heart and lungs are functioning. Your healthcare provider will understand these results and explain them to you.

Overview

It’s normal to feel stressed about the metabolic stress test. But don’t be scared or overly concerned about what will happen during the test. The test is a routine procedure that provides you and your healthcare provider with a wealth of information about the inner workings of your heart and lungs.

It may seem strange to have electrodes and devices attached to your body while you exercise. But keep in mind that each device collects important information that will help your doctor coordinate the care you need. Don’t hesitate to contact your doctor before your exam to find out how to prepare for the procedure or what to expect when you arrive at the lab.